As a process for producing an aromatic carbonic ester, there is generally known a process in which an aromatic monohydroxy compound such as phenol is reacted with phosgene in the presence of an alkali. This process, however, has a problem that deadly poisonous phosgene must be used and that a stoichiometric amount of an alkali salt is produced as a by-product.
Also known is a process for producing an aromatic carbonic ester by an ester interchange reaction of an aliphatic carbonic ester with an aromatic monohydroxy compound. Because this method requires continuous removal, by distillation, of an aliphatic alcohol or an aromatic alcohol produced as a by-product in order to proceed with the ester interchange reaction, a large amount of thermal energy is lost. Further, this process requires complicated steps and, thus, has a problem that the manufacturing steps as a whole, including a raw material preparation step and a by-product recycling step, are not economical.
Under these circumstances, development of a simple method for the production of a carbonic ester is desired. Thus, a process for producing an aromatic carbonic ester is proposed in which an aromatic monohydroxy compound to be esterified is subjected to oxidative carbonylation with carbon monoxide and oxygen in the presence of a catalyst. As typical catalysts used in this method, there are proposed a catalyst in which a palladium compound is combined with a copper compound and a base (Japanese Examined Patent Publications Nos. S61-8816 and S61-43338), a system in which a quinoline and an ammonium salt or an alkali metal or alkaline earth metal halide are used in addition to a palladium compound and a promoter (Japanese Unexamined Patent Publications Nos. S54-135743, S54-135744, H02-104564, H02-142754, H06-9505, H06-172268, H06-172269, H06-271506, H06-271509, Japanese Examined Patent Publication No. H06-57678, Japanese Unexamined Patent Publications Nos. H08-89810 and H08-193056), a catalyst system including a palladium compound, an alkali metal or alkaline earth metal halide, an iodide or an onium iodide compound and zeolite (Japanese Unexamined Patent Publication No. H01-165551) and a catalyst system including a palladium compound, an alkali metal or alkaline earth metal halide and activated carbon (Japanese Unexamined Patent Publication No. H08-92168). These catalysts are not fully satisfactory from the standpoint of economy with respect to the reaction rate of the oxidative carbonylation reaction. There is also proposed a method in which a palladium compound, a copper or lanthanoid compound, 2-hydroxypyridine and an aprotonic polar solvent are used (Japanese Unexamined Patent Publication No. H09-110804). Mainly because of the disuse of a solvent for the reaction, the yield of the method is low. Whilst the reaction proceeds using a halogenated organic solvent such as dichloromethane, the halogenated organic solvent is considered to adversely affect the environment.
As a process for producing a polycarbonate, there are generally known a method (solution method) in which an aromatic dihydroxy compound such as bisphenol A is directly reacted with phosgene, a method (ester interchange method) in which an aromatic dihydroxy compound such as bisphenol A is subjected to ester interchange with a carbonic diester such as diphenyl carbonate, and a method (melt method) in which a carbonic diester such as diphenyl carbonate is used as a carbonyl source and is heated and melted for reaction. However, the solution method has a problem that poisonous phosgene must be used and that the production apparatus is corroded by-product chlorine-containing compounds such as hydrogen chloride and sodium chloride. The ester interchange method requires complicated steps for the preparation of the carbonic diester raw material and that the manufacturing steps as a whole, including a raw material preparation step and a by-product recycling step, are not economical. The melt method requires heating for the production and melting of a carbonic diester and, thus, has a problem that the polycarbonate obtained is colored due to heating at elevated temperatures. As a process for producing an aromatic polycarbonate, there is disclosed, for example, a method in which an aromatic dihydroxy compound and carbon monoxide are reacted in the presence of a base and a selenium compound (Japanese Unexamined Patent Publication No. S55-92731). This method has a problem that selenium is deadly poisonous and that the reaction, which is a stoichiometric reaction, requires a large amount of selenium. As a new process for producing a polycarbonate, there is proposed a method by an oxidative carbonylation reaction using a palladium/redox agent/halogenated onium salt catalyst (for example, Japanese Unexamined Patent Publication No. S53-68744). With this method, only an oligocarbonate having a low degree of polymerization is obtained because the reaction rate is not sufficiently rapid. Another problem of this method is that a halogenated organic solvent which is considered to adversely affect the environment is used as a reaction solvent. With the foregoing background, production of a polycarbonate in an efficient and safe manner without adversely affecting the environment is desired.